1. Field of the Invention
This invention relates in general to motorcycle frames, and in particular to motorcycle frames of the type comprising a main frame with a pivotally mounted, dampened rear frame section.
2. Description of the Prior Art
In the 1970's Harley-Davidson developed the frame for its Softail.RTM. motorcycles. The typical frame for Harley-Davidson Softail.RTM. motorcycles is shown in U.S. Pat. No. 4,022,484. As shown in FIGS. 1-3 of U.S. Pat. No. 4,022,484, it is characterized by a main frame (2) and a rear frame (3) (often referred to as a swingarm) which is pivotally attached to the main frame. A damping means also couples the main and rear frames.
The frame shown in FIGS. 1-3 of U.S. Pat. No. 4,022,484 is generally representative of prior art frames for Softail.RTM. motorcycles. Namely, the main contoured members (13) connect the secondary longitudinal members (12) to the lower longitudinal members (7). The swingarm (3) has rear contoured members (14) such that when the swingarm (3) is mounted to the main frame (2), the rear contoured members (14) are located inward of the main contoured members (13).
Prior art Softail.RTM. motorcycle frames (such as that shown in FIGS. 1-3 of U.S. Pat. No. 4,022,484), were designed such that the drive belt, chain, or other drive member (not shown in U.S. Pat. No. 4,022,484) is located interiorly of both the main contoured member (13) and the rear contoured member (14). When the drive belt on motorcycles using this type of frame needs to be replaced, the swingarm (3) must be removed, requiring considerable labor.
Also, if prior art Softail.RTM.-type frames are adapted to accommodate large rear tires, the resulting width of the tire, the drive belt, and the main and rear contoured members results in the distance between the secondary longitudinal members (see FIGS. 1-3 of U.S. Pat. No. 4,022,484) being rather large. This can be uncomfortable for the rider.
Also, the load path between the transmission plate and the main contoured members in prior art Softail.RTM.-type motorcycle frames is rather long. The load is transferred from the transmission plate to the lower longitudinal members, and then from the lower longitudinal members to the main contoured members.
Finally, the prior art Softail.RTM.-type motorcycle frames are clearly identifiable as such because of the visibility of the main contoured members.